There are a lot of ppl on here that box 5 different classes even, and do quite well. I'd suggest finding who they are from the Who... Where... thread then do an advanced search for their posts and dig for stuff they've probably already brought up and worked through.

You're definitely jumping in the deep end but it sounds like you'd already built up these toons and are now just trying to figure out how to play them together which makes sense. Personally I've somewhat abandoned by warrior/priest/warlock that are 70 and started over with 4sham+pally.